How to use it
- Enter room length and width.
- Pick the sun exposure.
- Enter how many people regularly use the room.
- Choose whether it's a kitchen.
The formula
Base BTU from the ENERGY STAR area chart
−10% for shade, +10% for strong sun
+600 BTU per person over two; +4,000 BTU for a kitchen
Worked example
| Room length | 15 ft |
| Room width | 20 ft |
| Sun exposure | Normal |
| People who regularly use the room | 2 |
| Room is a kitchen | No |
Result
| Cooling capacity | 7,000 BTU/hr |
| Tons of cooling | 0.58 tons |
| Room area | 300 ft² |
Tips before you order
- An oversized AC cools quickly but leaves the room clammy because it doesn't run long enough to remove humidity.
- Whole-house systems need a Manual J load calculation instead.
Questions
What size AC for a 300 sq ft room?
About 7,000 BTU/hr under normal conditions.